1. Field of the Invention
The present invention relates to the field of image processing and, more particularly, to a de-ring system and method for reducing the overshooting and undershooting of video signal in a scaler.
2. Description of Related Art
The resolution of a video source is usually a fixed value in a liquid crystal television. Thus, the image of a video source has to be properly scaled for display in panels with different resolutions. U.S. Pat. No. 5,739,867 granted to Eglit for a “Method and apparatus for upscaling an image in both horizontal and vertical directions” has disclosed an image scaling technique for use in a liquid crystal display.
In the process of scaling, a filter is usually used to perform the scaling operation. Because of the filter, overshooting or undershooting is likely to appear in the image after filtering during the image processing. Thus, a ringing is easily generated in the process of scaling.
A method for deringing is provided in the specification Annex F of MPEG4. The maximum and the minimum of the whole image block is obtained first, and a threshold value is obtained based on the maximum and the minimum. Then, the method determines whether each pixel of the image block needs to perform deringing based on the threshold value, and if it needs, a weighted mask operation is performed for the pixel to smooth the pixel and its adjacent pixels.
However, MPEG4 only discloses the typical deringing technique. When the typical deringing technique is applied to the scaler, high frequency signals may be attenuated, resulting in, for example, blurring the edge of image, or a line buffer has to be added after the scaler to deal with new data. Therefore, it is desirable to provide a deranging system and method to mitigate and/or obviate the aforementioned problems.